PHYS 1407 – Conceptual Physics II
Test #2 Review Questions
1. At the security area of an airport, you walk through a weak ac magnetic field inside a coil of wire. What is the result of a small piece of metal on your person that slightly alters the magnetic field of the coil?
2. a) If you turn a generator faster, will the voltage produced be greater less or the same? b) Explain your answer.
3. Neon signs need high voltages to operate. The primary side of a transformer has 100 turns. How many turns does the secondary side need if you want to step up 120 V to 12000 V?
4. A magnet is placed through a loop of wire as shown. a) What will happen in the coil as the magnet first enters the coil. b) What will be the direction of the current? c) As the S pole of the magnet exits the coil, what direction is the current? d) Explain your answers.
5. A magnet is dropped through a closed coil. a) What happens in the coil? b) Why?
6. A long straight wire is next to a closed loop of wire as shown. Initially no current flows in either wire. A switch will be thrown and current will strat to flow in the long straight wire. Three students are discussing if anything will happen in the loop of wire.
Student A: “Nothing will happen in the loop. The current was turned on in the long wire.”
Student B: “As the current starts to flow in the wire there will be a changing magnetic field through the loop. For a brief time, a current will flow.”
Student C: “Once the current flows in the long straight wire, a magnetic field will pass through the loop. A steady current will flow in the loop.”
a) With which student do you agree?
___ I don’t agree with any of them.
b) Carefully explain your reasoning.
7. a) Sketch a picture of an electromagnetic wave. b) Label the electric and the magnetic field. c) What is the speed of the wave in vacuum?
8. a) How are x-rays, light, and radio waves similar? b) How are they different?
9. A radio station operates at 103,500,000 Hz. a) What is the wavelength of the waves broadcast by this station? b) How long does it take for the waves to travel 20 km (20,000 m) from the broadcast antenna to a car driving along the freeway?
10. a) Which has a longer wavelength, red light or violet light? b) Which has a higher frequency? Explain.
11. The table below gives the wavelength of light emitted by some atoms when excited. Rank the frequency of the light from greatest to least. Put any ties on the same line. Not all blanks have to be used.
Argon 519 nm
Mercury 436 nm
Hydrogen 653 nm
Sodium 589 nm
Helium 389 nm
Greatest Frequency 1 ____ 2____ 3____ 4_____ 5 ____ 6 ____ Least Frequency
Carefully explain your reasoning.
12. A student views a chair through a green filter and the chair appear green. The student makes the following statement.
Student: “Since the chair appears green through the green filter, the chair must be grain.”
a) What if anything is wrong with the student’s statement?
b) Explain your reasoning.
13. White light shines on chair and it appears blue. a) Predict what color it would appear if the following colors of light were shined on it.
i) red, ii) green, iii) blue iv) yellow v) cyan vi) magenta
b) Carefully explain your reasoning.
14. Complete the following when the following colors of light are added.
i) Red + Blue + Green =
ii) Red + Blue =
iii) Red + Green =
iv) Blue + Green =
v) Blue + Yellow =
vi) Cyan + Red
vii) Magenta + Green =
15. A flashlight is shined through a red filter and then a green filter. a) What color is the light after being transmitted through the second filter? b) Explain.
16. A flashlight is shined through a certain plastic that tends to absorb red light. If you look at the plastic, what color will it appear? Explain?
17. Smoke from a camp fire appears blue near the flame but tends to appear white or black further up. a) Why does the smoke appear blue near the flame? b) Why does the smoke appear white or black higher up?
18. Light is incident on glass at an angle of 45° as shown. a) Sketch the path of the light which is reflected from the glass. b) What is the angle of reflection? c) Sketch the path of the light which is transmitted through the glass. d) How does the refracted angle compare to the incident angle. Why?
19. A ray of light is incident on a mirror at an angle of 40°. a) What is the reflected angle? b) Make a sketch showing the incident and reflected angles.
20. a) What is the law of reflection. b) Draw a diagram to illustrate it
21. Light is incident on a piece of glass from air as shown. Sketch the path of the light inside the glass and as it exits the glass on the other side.
22. The following is a portion of a painting by Manet called “The Bar at the Folies-Bergere”. It shows a bartender facing you while standing in front of a plane mirror. The painting is famous for how it distorts reality in order to convey a story. In particular there are a number of things wrong with the image seen in the mirror. Describe some of them.
23. Complete the diagrams showing how each of the following lenses focuses incident parallel rays of light.
24. A student observes parallel rays incident on several lenses. In the two figures below, place in the correct type of lens.
25. A student holds a screen in front of a lens and sees a spot of light which gets larger as she moves the screen away from the lens. When she looks through the lens, she sees the image of the light source. At what kind of image is she looking? Explain.
26. A student holds a lens in front of his eyes and views the image of a distant object. The image appears small and upside down. a) Is the image real or virtual? Explain how you know. c) If the student used the same lens and viewed the image of an object that was very close (closer than the focal point) would the image be upright or upside down? d) Explain how you know.